Home | History | Annotate | Download | only in dom 
      1 /*
      2  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
     17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
     21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24  *
     25  */
     26 
     27 #ifndef ActiveDOMObject_h
     28 #define ActiveDOMObject_h
     29 
     30 #include "core/dom/ContextLifecycleObserver.h"
     31 #include "wtf/Assertions.h"
     32 
     33 namespace WebCore {
     34 
     35 class ActiveDOMObject : public ContextLifecycleObserver {
     36 public:
     37     ActiveDOMObject(ExecutionContext*);
     38 
     39     // suspendIfNeeded() should be called exactly once after object construction to synchronize
     40     // the suspend state with that in ExecutionContext.
     41     void suspendIfNeeded();
     42 #if ASSERT_ENABLED
     43     bool suspendIfNeededCalled() const { return m_suspendIfNeededCalled; }
     44 #endif
     45 
     46     // Should return true if there's any pending asynchronous activity, and so
     47     // this object must not be garbage collected.
     48     //
     49     // Default implementation is that it returns true iff
     50     // m_pendingActivityCount is non-zero.
     51     virtual bool hasPendingActivity() const;
     52 
     53     // These methods have an empty default implementation so that subclasses
     54     // which don't need special treatment can skip implementation.
     55     virtual void suspend();
     56     virtual void resume();
     57     virtual void stop();
     58 
     59     void didMoveToNewExecutionContext(ExecutionContext*);
     60 
     61 protected:
     62     virtual ~ActiveDOMObject();
     63 
     64     template<class T> void setPendingActivity(T* thisObject)
     65     {
     66         ASSERT(thisObject == this);
     67         thisObject->ref();
     68         m_pendingActivityCount++;
     69     }
     70 
     71     template<class T> void unsetPendingActivity(T* thisObject)
     72     {
     73         ASSERT(m_pendingActivityCount > 0);
     74         --m_pendingActivityCount;
     75         thisObject->deref();
     76     }
     77 
     78 private:
     79     unsigned m_pendingActivityCount;
     80 #if ASSERT_ENABLED
     81     bool m_suspendIfNeededCalled;
     82 #endif
     83 };
     84 
     85 } // namespace WebCore
     86 
     87 #endif // ActiveDOMObject_h
     88